This invention relates generally to the field of pulmonary treatment. More particularly, the invention relates to inhibiting hypersecretion of mucus in lungs and airways by the administration of an EGF-R antagonist. In addition, this invention also relates to methods for the development or assessment of candidate agents capable of inhibiting hypersecretion of mucus in the lungs.
In the conducting airways of the respiratory system, the mucociliary system serves as the primary defense mechanism to move inhaled particles or infectious agents out of the airways in the lungs. In addition, substances present in airway fluids serve to limit the toxicity of the particles and to inactivate infective agents. The physical mechanism of coughing serves to expel the mucus from the airway passages (see e.g., xe2x80x9cFoundations of Respiratory Care,xe2x80x9d Pierson and Kacmarek, eds. (1992) Churchill Livingstone Inc. New York, N.Y.; xe2x80x9cHarrison""s Principles of Internal Medicinexe2x80x9d, Fauci et al., eds. (1997) 14th Edition, McGraw Hill, New York, N.Y.).
The mucociliary system consists of ciliated epithelial cells, epithelial goblet cells, and serous and mucous cells located in submucosal glands. The cilia are surrounded by an aqueous layer (periciliary fluid) secreted into the lumen of the airway passage by the active transport of chloride and the passive movement of water across the epithelium. The cilia make contact with the mucus floating on this aqueous layer, and via a unidirectional propelling motion provide for movement of mucus toward the glottis (see Pierson and Kacmarek, supra and Fauci, et al., supra). Mucus is produced by the epithelial goblet cells and submucosal gland cells and is secreted into the lumen of the airway after degranulation.
While mucus generally facilitates the clearance of inhaled particles or infectious agents, hypersecretion of mucus in the airways may cause progressive airway obstruction. In peripheral airways, cough is ineffective for clearing secretions. Furthermore, because of their small dimensions, small airways containing many goblet cells are especially vulnerable to airway plugging by mucus. Airway hypersecretion affects a substantial number of individuals; it is seen in a variety of pulmonary diseases, such as chronic bronchitis, acute asthma, cystic fibrosis, and bronchiectasis.
Hypersecretion of mucus is the major symptom in patients with chronic obstructive pulmonary disease (COPD) and defines the condition (i.e. chronic cough and sputum production). This condition alone affects 14 million Americans and can cause progressive disability and death. It has been estimated that asthma affects at least 4% of the U.S. population and accounts for at least 2000 deaths annually (Pierson and Kucmarek, supra). During an acute asthmatic event, the bronchial walls swell, mucus volume increases and bronchial smooth muscle contracts, resulting in airway narrowing. As a result of hypersecretion in acute asthma, extensive mucus plugging can be a major cause of morbidity and mortality.
Hypersecretion has also been implicated in cystic fibrosis, which is one of the most common, fatal, genetic diseases in the world. Cystic fibrosis is an autosomal recessive disease that causes the airway mucosal cell to become unresponsive to cyclic-AMP-dependent protein kinase activation of the membrane chloride ion channels (Pierson and Kacmarek, supra and Fauci, et al., supra). The subsequent electrolyte imbalance reduces the level of hydration of the airway mucus, thus resulting in highly viscous mucus in the lungs of an individual afflicted with cystic fibrosis. Hypersecretion obstructs the air passages of individuals with cystic fibrosis, further compromising lung function.
Other disease involving hypersecretion include chronic obstructive lung disorder (COPD). Oxidant stress plays an important role in the pathogenesis of COPD. Cigarette smoke, which generates oxygen free radicals, is strongly implicated in the pathogenesis. Neutrophils are often seen at site of inflammation in COPD, and interestingly, oxygen free radicals are known to be released by neutrophils during activation.
Mechanical intubation is often necessary in order to provide assisted ventilation to patients with various pulmonary diseases. A tube is introduced via the oropharanx and placed in the trachea. To prevent leaking of air around the endotracheal tube, a balloon is inflated around the tube in the lower trachea, which may abrade the epithelium and cause goblet cell metaplasia. Wounding of epithelium leads to repair processes, which can result in abundant mucus secretion. Such prolonged tracheal intubation in patients can lead to deleterious effects due to hypersecretion.
As a result of the high levels of mucus in the lungs of patients with hypersecretory pulmonary diseases, mucosal clearance is reduced. Pathological agents such as bacteria, e.g. Pseudomonas aeruginosa, often establish colonies within the mucus, resulting in frequent lung infection.
Classical modalities of treating individuals afflicted with airway hypersecretion include antibiotic therapy, bronchodilators (e.g., methylxanthines, sympathomimetics with strong xcex22 adrenergic stimulating properties, anticholinergics), use of systemic or inhaled corticosteroids, primarily in asthma, liquefaction of the mucus by oral administration of expectorants, e.g. guaifenesin, and aerosol delivery of xe2x80x9cmucolyticxe2x80x9d agents, e.g. water, hypertonic saline solution (see Harrison""s, supra). A newer therapy for cystic fibrosis is the administration of DNAse to target the DNA-rich mucus or sputum (Shak, et al. (1990) Proc. Natl. Acad. (USA) 87:9188-9192; Hubbard, R. C. et al. (1991) N. Engl. J. Med. 326:812). In addition, chest physical therapy consisting of percussion, vibration and drainage are also used to facilitate clearance of viscous mucus. Lung transplantation may be a final option for those with severe pulmonary impairment. Therefore, more efficacious or alternative therapy to target the mucosal secretions is needed. Specifically, there is a need for a specific modality that will reduce the formation of mucus secretions in the airways.
Relevant Literature
The use of EGF inhibitors to block the growth of cancer cells is reviewed by Levitski (1994) Eur J Biochem. 226(1): 1-13; Powis (1994) Pharmac. Ther. 62:57-95; Kondapaka and Reddy (1996) Mol. Cell. Endocrin. 117:53-58.
Hypersecretion of mucus in airways is an adverse symptom of a number of different pulmonary diseases. The secretion results from the degranulation of goblet cells, the proliferation of which is promoted by stimulation of epidermal growth factor receptors (EGF-R). The present invention treats pulmonary hypersecretion by administering therapeutic amounts of EGF antagonists, preferably kinase inhibitors. The antagonists may be in the form of small molecules, antibodies, or portions of antibodies that bind to either EGF or its receptor. In another aspect of the invention, in vitro and in vivo methods predictive of the therapeutic potential of candidate agents to inhibit hypersecretion of mucus are provided.
A primary object of the invention is to provide a method of treating diseases involving hypersecretion of mucus in lungs.
Another object of the invention is to provide formulations useful in the treatment of diseases that result in hypersecretion of mucus.
Yet another object of the invention is to provide an in vitro assay for the screening of candidate agents that inhibit hypersecretion of mucus, where the method involves the steps of (i) contacting an in vitro model of goblet cell proliferation with EGF or the functional equivalent thereof; (ii) subsequently contacting the in vitro model with a candidate agent; and (iii) assessing goblet cell proliferation, wherein inhibition of goblet cell proliferation is indicative of the candidate agent""s therapeutic potential.
Another object of the invention is to provide an in vivo assay for the screening of candidate agents that inhibit hypersecretion of mucus, where the method involves (i) creating an animal model of hypersecretory pulmonary disease by inducing EGF-R, e.g. with tumor necrosis factor-alpha (TNF-xcex1); (ii) stimulating the induced EGF-R with its ligand, e.g. transforming growth factor alpha (TGF-xcex1) or EGF, to produce mucin producing goblet cells; (iii) treating with a candidate agent; and (iv) assessing goblet cell proliferation or mucus secretion, wherein an inhibition of goblet cell proliferation or mucus secretion is indicative of the candidate agent""s therapeutic potential.
A further object of the invention is to provide in vitro and in vivo assays for the screening of EGF-R antagonists that inhibit hypersecretion of mucus.
An advantage of the invention is that it provides a means for preventing excessive formation of mucus in pulmonary airways.
A feature of the invention is that a range of different types of antagonists can be used to block the effects of EGF and/or TGF-xcex1 and their interaction with EGF-R.
An aspect of the invention is formulations of EGF antagonists for reducing formation of mucus secretion in the airways of a mammalian patient, preferably a human patient.
Another object of the invention is a method of pulmonary delivery of EGF antagonists for reducing mucus secretions in the airways of a mammalian patient, preferably a human patient.
Another object of the invention is to provide a method for treating a range of different diseases which have as a symptom the excess formulation of mucus secretions in the airways. These diseases include, without limitation, chronic bronchitis, acute asthma, cystic fibrosis, bronchiectasis, chronic obstructive lung disease, hypersecretion resulting from epithelial damage such as allergic stimuli or mechanical abrasions, and nasal hypersecretion.
These and other objects, advantages, and features of the invention will become apparent to those persons skilled in the art upon reading the details of the treatment methods, and in vitro and in vivo assay methods, as more fully described below.